The invention relates to a dispenser for media. These are particularly liquid, but may also be or contain a paste, a powder, a gas or the like. Thus the media are flowable or trickling or non-flowable. The dispenser is held and actuated single-handedly. All or almost all components, particularly the exposed components, are injection-molded or made from plastics.
The dispenser may resuck medium from a reservoir during a working or stroke cycle or may contain, in a separate reservoir chamber, serval premeasured doses of the medium to be discharged in sequence. Preferably the dispenser is made for a single unidirectional stroke or medium discharge and then emptied. To prevent aging, chemical change or contamination of the medium the reservoir chamber is closed, not only tightly against the presence of germicides but also the medium is maintained in contact with only materials which avoid either chemical reactions with the medium or a physical change by contact with the medium. This is difficult to achieve with usual thermoplastic or other plastics materials such as polythene or with elastomers such as rubber, chlorinated or bromobutyl rubber.
The dispenser may be accidentally actuated by external forces when prevented from actuation merely by friction, e.g. by a catch. This applies irrespective of whether the reservoir chamber is closed or not by a stopper or the like such as pump piston which is primarily separate from a piston rod and then connected thereto. Even positive prevention of actuation may be accidentally released e.g. by mutual rotary motion of the two dispenser units.